Method for determining traffic related information

ABSTRACT

The invention relates to a method for determining traffic related information within a traffic system with the aid of mobile detectors ( 1 ), particularly from vehicles selected at random. According to the invention, the information which is used for determining the traffic situation is at least the standard deviation (σ) of the driven speed (v i ) of the mobile detector ( 1 ) compared to the average speed (v m ) of the mobile detector ( 1 ) on a section of a road (A B), and/or the sum (S) of the stationary time on said section of a road (A-B).

[0001] The invention concerns a method for determining traffic situation information within a traffic system using mobile detectors, in particular vehicles of a random-sample fleet, that have a terminal; a control center for determining traffic situation information within a traffic system that obtains, from at least one mobile detector, data regarding its geographic position; a terminal in a mobile detector that contains at least one position identification device or is connected thereto, and encompasses a data processing device and a device for data exchange with the control center; as well as a software program product that can be loaded directly into an internal memory of a control center and/or of the terminal of a mobile detector.

[0002] The acquisition and description of a traffic situation is an essential task in the field of traffic telematics, the goal of which, for example, is to inform traffic participants about situations with traffic impediments and to rectify such situations and, if applicable, prevent them by appropriate predictive diversion of traffic participants onto less-crowded routes. Another task is that of determining information for traffic planning and road system planning.

[0003] A wide variety of approaches to determining traffic information is known. German Unexamined Application DE 195 08 486, for example, discloses a method for determining traffic situation data or road status data in which individual random-sample vehicles, referred to as “floating cars,” transmit predetermined vehicle data and associated position data to a traffic control center. The traffic control center determines the traffic situation by way of the received data based on specific algorithms. German Unexamined Application DE 195 21 919 A1 proposes a method for transmitting traffic situation information in which the vehicle and position data that are acquired are already allocated, in the vehicle operating as detector, to at least one predefined category of vehicle and position data that correspond to a specific typical vehicle behavior. These categories are referred to as “vehicle behavior patterns.” The associated vehicle behavior pattern is transferred with the position data of the vehicle, at least partially in coded form, to the traffic control center. EP 789 341 A1 further purposes, in order to determine traffic situation information, to utilize the speed of the vehicle as vehicle data in the terminal of the mobile detector, by continuously acquiring it and evaluating it in the terminal by comparison with a limit speed as reference in the detector, so that when said speed falls below the limit speed, a change in traffic status lying below the threshold is recognized. The terminal, which is then in the evaluation state t\0, then checks the acquired speed values by comparison with the limit speed and, after a time t\0+t\1 has elapsed, interprets the overall traffic condition on the route segment as a traffic disruption if the mobile detector is being driven at a speed lower than the stored limit speed. If a traffic condition has been analyzed by the terminal as disrupted, an appropriate data telegram is generated and is transmitted via a mobile radio network to the traffic control center.

[0004] The disadvantage of the known methods is principally that a large number of false and/or irrelevant messages are generated; in particular, long waits at traffic lights, barriers, etc. in urban areas, as well as deceleration actions before encountering rural population centers, are detected as traffic disruptions and are forwarded to customers.

[0005] It is the object of the invention to carry out the determination of traffic situation information in such a way that the quantity of false and/or irrelevant traffic situation information is further reduced, and an accurate picture of the traffic situation is obtained.

[0006] The object of the invention is achieved by way of the features of claims 1, 18, 21, and 24. Advantageous embodiments and developments are presented in the dependent claims.

[0007] Provision is made according to the invention to use, for traffic situation assessment using mobile detectors, at least the standard deviation, i.e. the average deviation, of the speed being driven by the mobile detector from the mean speed of the mobile detector on a route segment, and/or the stand still times on the route segment being traveled.

[0008] The processable data for the route segments or the road system that are employed for traffic situation assessment are generated, for example, using a method as described in DE 100 52 109.

[0009] According to an advantageous embodiment of the invention, the following steps are performed in this context. In a preferably first method step, the mean speed of a mobile detector on at least one route segment being traveled by it is determined. A determination is additionally made of the standard deviation of the speed being driven by the detector from the mean speed or the average speed on the route segment being traveled, and/or of the sum of the stand still times of the mobile detector with respect to the travel time of the mobile detector on the route segment, the sum of the travel times preferably being indicated in proportion to the travel time.

[0010] The determined standard deviation of the route segment being traveled, as a function of the mean speed on the route segment being traveled, is compared to at least one boundary profile that is defined on the basis of the standard deviation and the mean speed. In other words, a point in a coordinate system constituted from the standard deviation and mean speed, that lies e.g. in a region next to or on the at least one boundary profile, is defined from the standard deviation and the mean speed.

[0011] Additionally or solely, a comparison can be made of the sum of the stand still times in proportion to the travel time on the route segment being traveled, as a function of the mean speed on the route segment, to at least one boundary profile that is defined with reference to the sum of the stand still times on the route segment being traveled and the mean speed. In other words, once again a coordinate system is constituted from the ratio of the sum of the stand still times to the travel time on the predefined route segment and the mean speed on the route segment. At least one boundary profile for the definition of traffic conditions is determined in this coordinate system, and the coordinate point that is constituted from the sum of the stand still times for the travel time and the mean speed is described in the coordinate system. In a further method step, a determination is made of the traffic situation on the route segment on the basis of the comparison of the standard deviation as a function of the mean speed, and/or on the basis of the comparison of the sum of the stand still times in proportion to the travel time as a function of the mean speed, to the respective boundary profile. Each of the boundary profiles preferably defines the boundary between two traffic conditions.

[0012] According to a preferred development, multiple boundary profiles that define various traffic conditions—such as “jammed,” “dense,” “slow-moving traffic,” or “clear”—can be provided both for the standard deviation as a function of the mean speed and for the sum of the stand still times as a function of the mean speed.

[0013] To prevent so-called “oscillations” about a boundary profile, the boundary profiles can exhibit a so-called hysteresis; in other words, a different value or value profile of the boundary profile is to be used depending on the traffic condition from which a change in the boundary profile proceeds.

[0014] An embodiment of the invention furthermore provides for the boundary profiles for definition of the traffic conditions to be stipulated on the basis of road type (expressway, secondary road, etc.). The possibility also exists, however, of defining the boundary profiles on a route-dependent basis. Parameters such as curve radii, hills, etc. can play a role here.

[0015] In a development of the invention, the invention further provides for the boundary profiles to be defined on the basis of infrastructure (intersections, traffic lights, on- and off-ramps, type of development along the route segment, etc.). A time-dependent definition of the boundary profiles is also possible; for example, the boundaries provided during rush hours can be different from those on weekends.

[0016] A development provides for the boundary profiles to be defined not statically but dynamically: if the situation on a route segment changes, the boundary profiles are adapted to the particular situation.

[0017] According to an embodiment of the invention, provision can be made for a traffic situation determination to be made at least on the basis of the maximum permitted speed on a route segment, on the basis of the standard deviation as a function of the mean speed, and/or on the basis of the sum of the stand still times as a function of the mean speed. Preferably, therefore, on expressways and highways a traffic situation determination is made on the basis of the standard deviation, and on city streets a traffic situation determination is made on the basis of stand still times on the route segments. Traffic situation determinations on the basis of the standard deviation and the stand still times are, however, also conceivable.

[0018] Another embodiment of the invention provides for a traffic situation determination to be made in at least infrastructure-dependent fashion on the basis of the standard deviation as a function of the mean speed, and/or on the basis of the sum of the stand still times as a function of the mean speed.

[0019] Provision can furthermore be made for the acceleration behavior of the mobile detector additionally to be employed for traffic situation determination. This has the advantage that a more accurate distinction can be distinguished between traffic-light phases and a jam on a route segment.

[0020] According to the invention, the traffic situation determination can be carried out both in a control center and in the mobile detector. If the determination is made in the control center, the respective mobile detector sends at least its time-related position data to the control center, which can determine speeds therefrom. Provision can also be made, however, for the respective mobile detector additionally to send its speed data. If the traffic situation is determined directly by the mobile detector, an embodiment provides for the mobile detector to receive data about an expected or current traffic situation, and for it to send data regarding the traffic situation to the control center only in the event of a change in the traffic situation. The possibility also exists for the mobile detector not to transmit its data to the control system during the journey, but rather to transfer the data after completion of the journey. A method of this kind can be used, for example, in traffic route planning.

[0021] According to the invention, the control center for determining traffic situation information is embodied in such a way that it carries out or can carry out the method according to the present invention. It has a data communication connection to the mobile detectors, by way of which it obtains position data, and optionally vehicle status data, of the mobile detector.

[0022] The invention furthermore concerns a terminal in a mobile detector that contains at least one position identification device or is connected thereto, and encompasses a data processing device and a device for data exchange with a control center, the terminal being configured to carry out the method according to the present invention.

[0023] An embodiment of the terminal provides for the terminal to determine its speed from its time-related position data. It can, however, receive the speed of the mobile detector from a vehicle speed sensor or from vehicle status data.

[0024] The invention further concerns a software program product that can be loaded directly into an internal memory of the control center and/or of the terminal of a mobile detector, and that encompasses program steps with which the method steps in accordance with the method according to the present invention are carried out and/or are executable when the program product runs in the control center and/or in the terminal.

[0025] The invention is described in more detail below with reference to an exemplified embodiment. In the attached drawings:

[0026]FIG. 1 is a block diagram of a system for determining the traffic situation;

[0027]FIG. 2 shows an example of determination of the traffic situation using the standard deviation; and

[0028]FIG. 3 shows an example of determination of the traffic situation by way of the sum of stand still times.

[0029]FIG. 1 depicts a system for acquiring traffic situation information on a route being traveled by at least one mobile detector 1, in particular a vehicle of a random-sample fleet. Terminal 1 a of a mobile detector 1 has a position identification device for determining the geographical coordinates of its instantaneous location, preferably a satellite-based sensing device 2; a data processing device 6; and a device 4 for bidirectional data communication with a corresponding communication device of a control center 3. By way of this data communication link, terminal 1 a communicates via a point-to-point procedure with control center 3, and in the simplest case sends its geographical coordinates, acquired in time-related fashion, to control center 3, which determines from the change over time in the geographical coordinates of mobile detector 1, using the method according to the present invention, the traffic situation on a route segment and/or the travel times on the route segment. Another possibility is that terminal 1 a, in data processing device 6, itself determines the speed of the mobile detector from the position data or receives it from an acquisition device, and by way of the method according to the present invention determines the traffic situation and, on the basis of predefined criteria, e.g. on the basis of a comparison with instantaneous and/or expected values with data of the relevant route segment, for example as generated according to a method such as the one presented in DE 100 52 109, sends it to control center 3. The data for the route segment or for a determination network for the traffic situation either are stored in data processing device 6 or are transferred to mobile detectors 1 via a communication procedure, for example on the basis of their position, from control center 3.

[0030] The method according to the present invention will be explained in more detail below by way of FIGS. 2 and 3, based on a concrete example. In this example, the traffic route system that is to be evaluated, which contains only the route segments of the actual road system that appear relevant for a traffic situation assessment, is subdivided into three road types. These are firstly the expressways and highways having a very high maximum permitted speed, secondary roads, and city streets having traffic signal systems and intersections.

[0031] In the exemplified embodiment, the standard deviation σ as a function of the mean speed v_(m) of mobile detector 1 on route segment A-B is employed for assessment of the traffic situation on the expressways and highways. For that purpose, the instantaneous speed v_(i) of mobile detector 1 is acquired, continuously or at defined time intervals, or is calculated from the change over time in the position data on route segment A-B; the mean speed v_(m) of mobile detector 1 on the route segment is determined therefrom; and from that, the standard deviation σ of the speed v_(i) being driven by mobile detector 1 from the mean speed v_(m) is determined.

[0032] The standard deviation σ is calculated using the following formula: $\sigma = \left( \frac{\sum\limits_{l = 0}^{n}\left( {{Vm} - {Vi}} \right)^{2}}{N\left( {N - 1} \right)} \right)^{1/2}$

[0033] where n is the number of time-related positions of the mobile detector that are determined.

[0034]FIG. 2a shows several curves for the speed v_(i) and mean speed v_(m) on route segment A-B for different traffic conditions. If the standard deviation σ as a function of the mean speed v_(m) is then calculated for each of the speed curves v₁, v₂, v₃, and is compared to various boundary profiles G1, G2, G3 that define different traffic conditions on route segment A-B, what is obtained is the traffic situation during the journey of mobile detector 1 along the route segment. During the journey along the route segment at speed v_(i), the mean speed v_(m1) was relatively low, but the standard deviation σ was very high because of the stop-and-go behavior of mobile detector 1; this is recognized as a “jam”. The journey at speed v₂ exhibits a mean speed v_(m) of approx. 80 km/h with a low standard deviation σ. This is recognized as “dense” traffic. The journey at speed v₃ exhibits a high mean speed v_(m) with a low standard deviation σ. Route segment A-B is “clear”. To prevent oscillations between two traffic conditions when recognizing the traffic situation, a hysteresis H was additionally introduced for each boundary profile.

[0035] For traffic situation determination on city streets, the problem exists that the traffic signal systems impose a pronounced stop-and-go behavior that must be distinguished from actual traffic jams. For this reason, on city streets it is advisable to perform a traffic situation acquisition using the sum of the stand still times on a route segment. FIG. 3a shows the speed curves v₄, v₅ for two journeys by mobile detectors 1 along a route segment A-B of a city street. As is evident, the stationary component S of travel time t on route segment A-B during the journey at speed v₅ is relatively large, and the mean speed v_(m) is low. If the stationary component S (as a percentage) as a function of the mean speed v_(m) is compared to boundary profiles G1 and G3 (FIG. 3b), it is apparent that the route segment was jammed. During the journey at speed v₄, on the other hand, the route segment was clear. Optionally, the standard deviation can be considered as an additional criterion for traffic situation determination on city streets.

[0036] On secondary roads with a maximum permitted speed of up to 100 km/h, a traffic situation determination should preferably be carried out by way of the standard deviation of the speed v_(i) being driven by the mobile detector from the mean speed v_(m), in which context both the number of boundary profiles G and their profiles may different by comparison with a traffic situation determination on expressways and highways. Provision can also be made for the traffic in the opposite direction, i.e. the traffic situation in the oncoming lane, and/or the acceleration of mobile detector 1, to be taken into account. It is additionally possible to take into account the stationary component, especially in borderline areas between two traffic conditions. 

What is claimed is:
 1. A method for determining traffic situation information within a traffic system using mobile detectors (1), in particular vehicles of a random-sample fleet, that have a terminal (1 a), wherein at least the standard deviation (σ) of the speed (v_(i)) being driven by the mobile detector (1) from the mean speed (v_(m)) of the mobile detector (1) on a route segment (A-B), and/or the sum (S) of the stand still times on the route segment (A-B) being traveled, are used as information for determining the traffic situation.
 2. The method as recited in claim 1, wherein the following steps are carried out: determining the mean speed (v_(m)) of at least one mobile detector (1) on at least one route segment (A-B) being traveled by it; determining the standard deviation (σ) of the speed (v_(i)) being driven by the mobile detector (1) from the mean speed (v_(m)) on the route segment (A-B) being traveled, and/or the sum (S) stand still times of the mobile detector (1) on the route segment (A-B) being traveled; comparing the standard deviation (σ) as a function of the mean speed (v_(m)) on the route segment (A-B) being traveled to at least one boundary profile (G) that is defined on the basis of the standard deviation (σ) and the mean speed (v_(m)); and/or comparing the sum (S) of the stand still times on the route segment (A-B) being traveled, as a function of the mean speed (v_(m)) on the route segment (A-B) being traveled, to at least one boundary profile (G) that is defined on the basis of the sum (S) of the stand still times on the route segment (A-B) being traveled and the mean speed (v_(m)) on the route segment (A-B); determining a traffic situation condition on the basis of the comparison of the standard deviation (σ) as a function of the mean speed (v_(m)) to the at least one boundary profile (G) that is defined on the basis of the standard deviation (σ) and the mean speed (v_(m)); and/or determining a traffic situation condition on the basis of the comparison of the sum (S) of the stand still times as a function of the mean speed (v_(m)) to the at least one boundary profile (G) that is defined on the basis of the sum (S) of the stand still times and the mean speed (v_(m)) on the route segment (A-B).
 3. The method as recited in claim 1 or 2, wherein the boundary profiles (G) define the boundary between two traffic conditions.
 4. The method as recited in one of claims 1 through 3, wherein multiple boundary profiles (G) are provided that are defined on the basis of standard deviation (σ) and the mean speed (v_(m)) on a route segment (A-B).
 5. The method as recited in one of claims 1 through 4, wherein multiple boundary profiles (G) are provided that are defined on the basis of the sum (S) of the stand still times on the route segment (A-B) being traveled and the mean speed (v_(m)) on the route segment (A-B).
 6. The method as recited in one of claims 1 through 5, wherein at least one of the boundary profiles (G) exhibits a hysteresis (H).
 7. The method as recited in one of claims 1 through 6, wherein for definition of the traffic conditions, the boundary profiles (G) are defined on the basis of road type.
 8. The method as recited in one of claims 1 through 7, wherein the boundary profiles (G) are defined on a route-dependent basis.
 9. The method as recited in one of claims 1 through 8, wherein the boundary profiles (G) are defined in infrastructure-dependent fashion.
 10. The method as recited in one of claims 1 through 9, wherein the boundary profiles (G) are defined in time-dependent fashion.
 11. The method as recited in one of claims 1 through 10, wherein the boundary profiles (G) are modifiable.
 12. The method as recited in one of claims 1 through 11, wherein at least on the basis of the maximum permissible speed on a route segment (A-B), a traffic situation determination is made on the basis of the standard deviation (σ) as a function of the mean speed (v_(m)), and/or on the basis of the sum (S) of the stand still times as a function of the mean speed (v_(m)).
 13. The method as recited in one of claims 1 through 12, wherein a traffic situation determination is made in at least infrastructure-dependent fashion on the basis of the standard deviation (σ) as a function of the mean speed (v_(m)), and/or on the basis of the sum (S) of the stand still times as a function of the mean speed (v_(m)) on a route segment (A-B).
 14. The method as recited in one of claims 1 through 13, wherein the acceleration behavior of the mobile detector (1) is additionally employed for traffic situation determination.
 15. The method as recited in one of claims 1 through 14, wherein the traffic situation determination is carried out in a control center (3) that receives at least time-related data for the position of the at least one mobile detector (1).
 16. The method as recited in one of claims 1 through 14, wherein a traffic situation determination is carried out in the terminal (1 a) of the mobile detector (1), and data about the traffic situation are sent to a control center (3) and or transferred thereto.
 17. The method as recited in claim 16, wherein the control center (3) sends data about an expected traffic situation to the mobile detector (1), and the mobile detector (1) transmits data regarding the determined traffic situation to the control center (3) substantially only in the event of a change in the expected traffic situation.
 18. A control center for determining traffic situation information within a traffic system, that obtains, from at least one mobile detector (1), data regarding its geographic position, wherein the control center (3) is embodied to carry out a method as defined in one of claims 1 through
 17. 19. The control center as recited in claim 18, wherein the control center (3) receives from the mobile detector (1) time-related data concerning its geographic position.
 20. The control center as recited in claim 18 or 19, wherein the control center (3) receives vehicle status data of the mobile detector (1), at least the instantaneous speed (v_(i)).
 21. A terminal in a mobile detector that contains at least one position identification device (2) or is connected thereto, and encompasses a data processing device (6) and a device (4) for data exchange with the control center (3), wherein the terminal (1 a) is configured to carry out a method as defined in one of claims 1 through
 17. 22. The terminal as recited in claim 21, wherein the terminal (1 a) determines the speed (v_(i)) of the mobile detector (1) from its time-related position data.
 23. The terminal as recited in claim 21, wherein the terminal (1 a) receives the speed (v_(i)) of the mobile detector (1) from a vehicle speed sensor, or determines it from vehicle status data.
 24. A software program product that can be loaded directly into an internal memory of the control center (3) and/or of the terminal (1 a) of a mobile detector (1), and that encompasses program steps with which the method steps in accordance with one of claims 1 through 17 are executed and/or are executable when the program product runs in the control center (3) and/or in the terminal (1). 